April Fool's Day (1986)

A group of eight college friends gather together at an island mansion belonging to heiress Muffy St. John to celebrate their final year of school. They soon discover that each has a hidden secret from their past which is revealed, and soon after, they turn up dead. Yet, are they really dead? Or is it just part of some very real and cruel April Fool's jokes? The hostess, Muffy, is the only one who apparently knows what's going on. But then again, is it really her doing the killing?